The present invention relates to a surface-releasing agent against sticking adhesives or, more particularly, to a surface-releasing composition against sticking adhesives having excellent repellency against water and oils and good transparency and capable of exhibiting excellent surface-releasability even against silicone-based sticking adhesives.
When it is desired to impart surface-releasability against sticking adhesives, as is well known, films or tapes of fluorocarbon resins are conventionally employed with or without embossing but the effectiveness thereof as a means for surface-releasing is limited. Although various kinds of fluorine-containing copolymeric resins are useful as a special industrial material in the applications including water-repellent textile finishing agents and protecting agents for external walls of building by utilizing the water-repellency and oil-repellency inherent in fluorine-containing organic compounds and sheathing material on optical fibers and material of contact lenses by utilizing the optical properties thereof. When such a fluorocarbon resin is used in the form of a film or in the form of a coating composition with an object to serve as a means for providing surface-releasability, however, the film or coating layer formed of the coating composition readily falls off the surface of the substrate body such as glass, paper, plastic, metal and the like due to the poor adhesiveness thereof to the substrate surface so that the object of surface-releasing cannot be achieved.
Accordingly, proposals have been made to use, as a principal ingredient of a surface-releasing agent against sticking adhesives, a copolymeric resin of a fluorinated alkyl vinyl monomer with maleic anhydride or a vinylic monomer having a hydroxy group, carboxyl group and the like usually considered to be effective to impart adhesiveness to the substrate surface. Although the copolymeric resin with a vinylic monomer has no adverse influences on the sticking power of a sticking adhesive, the surface releasability as an inherent characteristic of flourinated alkyl-containing resins cannot be fully exhibited thereby. Further, the copolymeric resin with maleic anhydride is disadvantageous because of the appearance of turbidity in a transparent substrate film coated therewith in addition to the decrease in the surface releasability when it is prolongedly exposed to an atmosphere of high humidity although substantial increase can be obtained in the adhesiveness of the resin to the substrate surface.
When the sticking adhesive is of the silicone-based type having particularly high sticking power among others, conventional surface-releasing agents known in the prior art are far from satisfactory so that there is no choice in the selection of surface releasing agents but to use the above described ones even though they are unsatisfactory.